Manufacturing method of piezoelectric vibrator unit, manufacturing method of liquid jet head, piezoelectric vibrator unit, and liquid jet head

ABSTRACT

Common internal electrodes  27  and segment internal electrodes  28  are laminated alternately with a piezoelectric material  29  between and a common external electrode  30  and a segment external electrode  31  are provided on the surface, forming a drive vibrator  24 . A free end part  24   a  of the drive vibrator  24  is formed with an active region L and can be expanded and contracted in the length direction of the vibrator. A piezoelectric material  29  of the outermost layer in the free end part  24   a  can be operated based on the potential difference between the external and internal electrodes and a portion of the active region L in the external electrode is used as a trimming portion with an effective length x varied by trimming.

This is a divisional of application Ser. No. 10/703,465 filed Nov. 10,2003 now U.S. Pat. No. 6,955,421, which is a divisional of Ser. No.09/748,104, now U.S. Pat. No. 6,732,414 filed Dec. 27, 2000; the entiredisclosure of the prior applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION

This invention relates to a liquid jet unit used in an industrialmachine, such as a manufacturing machine for manufacturing opticalfilters, and an image recording apparatus such as a plotter and aprinter, and a piezoelectric vibrator unit used in the liquid jet unit.This invention also relates to methods of manufacturing the liquid jetunit and the piezoelectric vibrator unit.

Industrial machines such as manufacturing machines and image recordingapparatuses such as plotters and printers are available, which employ aliquid jet head for ejecting liquid in the form of liquid droplets. Forexample, an industrial machine for manufacturing an optical filter isdesigned to eject color material in the form of liquid droplets onto afilter substrate using an ejection head (a kind of liquid jet head). Animage recording apparatus is designed to eject ink droplets from arecording head (a kind of liquid jet head) onto a printing or recordingmedium such as paper.

These industrial machines and image recorders require high accuracy forthe amount and speed of the ejected liquid droplets. For example, theoptical filter manufacturing machine must eject a proper amount (i.e. aproper ejection amount) of an color material droplet onto a properposition with high accuracy since the optical filter manufactured withthe industrial machine is used with a liquid crystal display, etc. Theimage recording apparatus requires high accuracy as to a position ontowhich an ink droplet is ejected, and an amount of the ejected ink, inorder to improve image quality and speed up the recording.

The liquid jet head, widely used in these industrial machines and imagerecording apparatuses, typically includes: a flow passage unit formedwith a plurality of ink flow passages each extending from a reservoirthrough a pressure chamber to a nozzle opening; and a piezoelectricvibrator unit being placed on the rear of the flow passage unit andhaving a plurality of piezoelectric vibrators provided in a one-to-onecorrespondence with the pressure chambers for changing the volumes ofthe corresponding pressure chambers. The liquid jet head ejects liquidfrom a nozzle opening by changing the volume of the correspondingpressure chamber using deformation (displacement) of the correspondingpiezoelectric vibrator.

The piezoelectric vibrator unit is manufactured, for example, accordingto the following procedure: First, common internal electrodes andsegment internal electrodes are laminated alternately with apiezoelectric material interposed between adjacent internal electrodesto manufacture a plate-like laminated substrate, and a common externalelectrode electrically conducted to the common internal electrodes and asegment external electrodes electrically conducted to the segmentinternal electrodes are formed on the surface of the laminated substrateto obtain a laminated member. After the base end side portion of thelaminated member is fixed to a fixing plate, the leading end sideportion of the laminated member is cut into a plurality of segments(piezoelectric vibrators) each having an extremely narrow width of about50 μm to 100 μm using a wire saw, a dicing saw, etc.

The piezoelectric vibrator unit thus manufactured is disposed in a statein which the displaceable surfaces of piezoelectric vibrators arecontacted with diaphragm parts for the pressure chambers, respectively.

Another type of the liquid jet head has piezoelectric vibrators that areprovided in the diaphragm parts for the pressure chambers, respectively.The liquid jet head of this type ejects liquid from a nozzle opening bychanging the volume of the corresponding pressure chamber usingdeformation (displacement) of the corresponding piezoelectric vibratorsimilarly.

The liquid jet head using the piezoelectric vibrator unit has anadvantage in that piezoelectric vibrators having identical displacementcharacteristic can be easily obtained because the piezoelectricvibration unit is manufactured such that the laminated member is cut toprovide the piezoelectric vibrators. Namely, a come-like piezoelectricvibrator is provided by cutting substantially the same piezoelectricvibrator unit. Therefore, since it is substantially the same one first,the variation in the characteristic between each piezoelectric vibratoris small. However, each piezoelectric vibrator obtained as a consequenceof cutting has an extremely narrow width, and therefore slight variationin width may occur. Since the piezoelectric vibrator is of laminatedtype, if a pinhole larger than the width of the piezoelectric vibratorexists in the internal electrode, the internal electrode is broughtpartially out of electric conduction by the presence of the pinhole. Inthe case of the industrial machine of which especially high precision isrequired, even if it is the small piezoelectric vibrator of variation,the small highly precise characteristic of variation is demanded morethan it. Thus, the width variation of the piezoelectric vibrators, thedefect of the internal electrode, and the like cause the piezoelectricvibrators to have sight varied displacement amounts.

In the case of the liquid jet head in which the piezoelectric vibratorsare provided in the diaphragm parts for the pressure chambers, thethickness, shape, etc., of piezoelectric material is likely to bevaried, and thus the displacement amounts of the piezoelectric vibratorsare varied largely in comparison to the case where the piezoelectricvibrators constitute the piezoelectric vibrator unit.

Such displacement amount variation of the piezoelectric vibratorsadversely affect the liquid ejection characteristic of the liquid jethead and thus is not preferable. For example, in the case of the opticalfilter manufacturing machine, the sizes of pixels forming the opticalfilter are varied depending on the respective nozzle openings, and inthe case of the image recording apparatus, the pixels deposited onto arecording medium are made non-uniform in size.

Further, the liquid ejection characteristic of the liquid jet head isalso changed due to the attachment state of the vibrator unit to theflow passage unit and the shape of the ink flow passage in the flowpassage unit.

To prevent these problems, it is conceivable to fill one scanning linewith liquid droplets ejected from a plurality of nozzle openings, butthis will lower the throughput since the liquid jet head needs to bescanned plural times to fill one scanning line.

This is particularly not preferable for the industrial machines sincethe lowered throughput results in lowered production efficiency and thusincreased cost of the product.

SUMMARY OF THE INVENTION

The present invention was made in order to solve the above-mentionedproblems, and an object of the present invention is to make uniform thedisplacement amounts of piezoelectric vibrators, and to thereby makeuniform the liquid ejection characteristic of a liquid jet head.

According to the present invention, one or more of piezoelectricvibrators, which will cause variation in liquid ejection characteristic,is subjected to a displacement amount adjustment treatment to makeuniform the displacement amounts of piezoelectric vibrators.

The present invention provides the followings:

(1) A manufacturing method of manufacturing a piezoelectric vibratorunit comprising a plurality of piezoelectric vibrators, each having, atleast in part, a laminate structure of electrodes and at least one layerof piezoelectric material, said manufacturing method comprising:

a displacement amount measurement step of measuring a displacementamount of each of the piezoelectric vibrators with respect to areference voltage; and

a displacement amount adjustment step of setting a treatment conditionfor at least one of the piezoelectric vibrators based on a result ofmeasurement by the displacement amount measurement step, and subjectingthe at least one of the piezoelectric vibrators to a displacement amountadjustment based on the thus set treatment condition, thereby making thedisplacement amounts of the piezoelectric vibrators uniform.

(2) The manufacturing method of (1), wherein:

the laminate structure includes an external electrode as an outermostone of the electrodes in a laminate direction, and an internal electrodethat is to be different in polarity from the external electrode and thatis confronted with the external electrode through a layer of thepiezoelectric material to form an active region,

the displacement amount adjustment includes a step of trimming a portionof the external electrode of the at least one piezoelectric vibrator,the portion being located within the active region.

(3) The manufacturing method of (2), wherein the displacement amountadjustment step includes setting a piezoelectric vibrator having thesmallest displacement amount with respect to the reference voltage as areference vibrator, and adjusting the displacement amounts of thepiezoelectric vibrators, other than the reference vibrator, to beidentical to the displacement amount of the reference vibrator.

(4) The manufacturing method of (2), wherein said displacement amountadjustment step includes setting a piezoelectric vibrator having thesmallest displacement amount with respect to the reference voltage as areference vibrator, and adjusting the displacement amounts of all thepiezoelectric vibrators to be identical to a target displacement amountsmaller than the displacement amount of the reference vibrator.

(5) The manufacturing method of any one of (2) to (4), wherein the stepof trimming includes trimming the portion of the external electrodeusing laser beam.

(6) The manufacturing method of any one of (2) to (5), furthercomprising:

laminating piezoelectric material layers and internal electrode layersalternately to provide a laminate substrate;

forming an external electrode layer on at least a surface of thelaminate substrate to provide a laminate member; and

at least partially cutting the laminate member to provide thepiezoelectric vibrators in the form of teeth of comb.

(7) The manufacturing method of (1), further comprising

a semi-saturation polarization treatment step, executed prior to thedisplacement amount measurement step, of polarizing the piezoelectricmaterial to put the piezoelectric material into a semi-saturationpolarization state, not into a saturation polarization state, andwherein

the displacement amount adjustment includes a re-polarization treatmentstep of re-polarizing the piezoelectric material of the at least onepiezoelectric vibrator in a direction from the semi-saturationpolarization state toward the saturation polarization state.

(8) The manufacturing method of (7), wherein the displacement amountadjustment step includes setting a piezoelectric vibrator having thelargest displacement amount with respect to the reference voltage as areference vibrator, and adjusting the displacement amounts of thepiezoelectric vibrators, other than the reference vibrator, to beidentical to the displacement amount of the reference vibrator.

(9) The manufacturing method of (7), wherein the displacement amountadjustment step includes setting a piezoelectric vibrator having thelargest displacement amount with respect to the reference voltage as areference vibrator, and adjusting the displacement amounts of all thepiezoelectric vibrators to be identical to a target displacement amountlarger than the displacement amount of the reference vibrator.

(10) The manufacturing method of any one of (7) to (9), wherein thesemi-saturation polarization state is set to be 90% of the saturationpolarization state.

(11) The manufacturing method of any one of (7) to (10), wherein atleast one of the semi-saturation polarization treatment step and there-polarization treatment step uses a voltage value applied to thepiezoelectric material as a variable, and adjusts the voltage value toobtain a desired degree of polarization.

(12) The manufacturing method of any one of (7) to (11), wherein atleast one of the semi-saturation polarization treatment step and there-polarization treatment step uses a time period, for which a voltageis applied to the piezoelectric material, as a variable, and adjusts thetime period to obtain a desired degree of polarization.

(13) The manufacturing method of any one of (7) to (12), wherein atleast one of the semi-saturation polarization treatment step and there-polarization treatment step uses a temperature of the piezoelectricmaterial as a variable, and adjusts the temperature to obtain a desireddegree of polarization.

(14) The manufacturing method of (1), further comprising:

a saturation polarization treatment step, executed prior to thedisplacement amount measurement step, of polarizing the piezoelectricmaterial to put the piezoelectric material into a saturationpolarization state,

wherein the displacement amount adjustment includes a spot heatingtreatment step of locally heating the piezoelectric material of the atleast one piezoelectric vibrator in a direction away from the saturationpolarization state.

(15) The manufacturing method of (14), wherein the displacement amountadjustment step includes setting a piezoelectric vibrator having thesmallest displacement amount with respect to the reference voltage as areference vibrator, and adjusting the displacement amounts of thepiezoelectric vibrators, other than the reference vibrator, to beidentical to the displacement amount of the reference vibrator.

(16) The manufacturing method of (14), wherein the displacement amountadjustment step includes setting a piezoelectric vibrator having thesmallest displacement amount with respect to the reference voltage as areference vibrator, and adjusting the displacement amounts of all thepiezoelectric vibrators to be identical to a target displacement amountsmaller than the displacement amount of the reference vibrator.

(17) The manufacturing method of any one of (14) to (16), wherein thespot heating treatment step includes heating the piezoelectric materialto a Curie temperature of the piezoelectric material or higher.

(18) The manufacturing method of any one of (14) to (17), wherein thespot heating treatment step includes locally applying a laser beam tothe piezoelectric material of the at least one piezoelectric vibrator.

(19) The manufacturing method of any one of (14) to (17), wherein thespot heating treatment step includes locally applying an infrared ray tothe piezoelectric material of the at least one piezoelectric vibrator.

(20) The manufacturing method of any one of (14) to (17), wherein thespot heating treatment step includes locally abutting a heating terminalagainst the piezoelectric material of the at least one piezoelectricvibrator.

(21) The manufacturing method of (1), further comprising:

a semi-saturation polarization treatment step, executed prior to thedisplacement amount measurement step, of polarizing the piezoelectricmaterial to put the piezoelectric material into a semi-saturationpolarization state, not into a saturation polarization state, andwherein

the displacement amount adjustment step includes a polarizationadjustment step of adjusting the polarization state of the piezoelectricmaterial of the at least one piezoelectric vibrator by selecting atleast one of a re-polarization treatment of re-polarizing thepiezoelectric material in a direction from the semi-saturationpolarization state toward the saturation polarization state and a spotheating treatment of locally heating the piezoelectric material topartially depolarizing the piezoelectric material.

(22) The manufacturing method of (1), wherein the displacement amountadjustment includes a heating polarization adjustment step of supplyinga polarization drive signal to the electrodes to charging anddischarging the piezoelectric material alternately and to generate heatfrom the at least one piezoelectric vibrator, and polarizing thepiezoelectric material of the at least one piezoelectric vibrator underthe heat thus generated.

(23) The manufacturing method of any one of (7) to (22), wherein thelaminate structure includes common internal electrodes and segmentinternal electrodes laminated alternately with a layer of thepiezoelectric material interposed between adjacent pair of the commonand segment internal electrodes to form an active region in a free endpart.

(24) The manufacturing method of (23), wherein each of the piezoelectricvibrators is displaced in a direction orthogonal to a laminationdirection by the action of an electric field.

(25) The manufacturing method of (23), wherein each of the piezoelectricvibrators is displaced in a lamination direction by the action of anelectric field.

(26) The manufacturing method of any one of (23) to (25), furthercomprising:

laminating piezoelectric material layers and internal electrode layersalternately to provide a laminate substrate;

forming an external electrode layer on at least a surface of thelaminate substrate to provide a laminate member; and

at least partially cutting the laminate member to provide thepiezoelectric vibrators in the form of teeth of comb.

(27) A manufacturing method of manufacturing a liquid jet headcomprising a plurality of piezoelectric vibrators, each having, at leastin part, a laminate structure of electrodes and at least one layer ofpiezoelectric material, and a plurality of liquid flow passagesrespectively formed for communication from a reservoir through pressurechambers to nozzle openings associated with the piezoelectric vibrators,wherein deformation of a piezoelectric vibrator causes deformation of arespective pressure chamber and changes liquid pressure in therespective pressure chamber to thereby eject liquid from a respectivenozzle opening, the manufacturing method comprising:

an ejection characteristic measurement step of applying the same drivesignal to all the piezoelectric vibrators to eject liquid from thenozzle openings, and measuring liquid ejection characteristic inone-by-one basis of the nozzle openings; and

an ejection characteristic adjustment step of setting a treatmentcondition for at least one of the piezoelectric vibrators based on aresult of measurement by the ejection characteristic measurement step,and subjecting the at least one piezoelectric vibrator to a displacementamount adjustment based on the thus set treatment condition, therebymaking the liquid ejection characteristic associated with the nozzleopenings uniform.

(28) The manufacturing method of (27), wherein the liquid ejectioncharacteristic includes a liquid ejection amount.

(29) The manufacturing method of (27), wherein the liquid ejectioncharacteristic includes a liquid ejection speed.

(30) The manufacturing method of (27), wherein the liquid ejectioncharacteristic includes an area of ejected liquid on an object.

(31) A piezoelectric vibrator unit comprising a plurality ofpiezoelectric vibrators, each having at least in part, a laminatestructure including first and second internal electrodes laminatedalternately with a layer of piezoelectric material interposed betweenadjacent pairs of the first and second internal electrodes to an activeregion in a free end part, a first external electrode electricallyconducted to the first internal electrodes and a second externalelectrode electrically conducted to the second internal electrodes,wherein a potential difference is given to the piezoelectric material inthe active region through the first and second external electrodes toactivate the piezoelectric material, thereby displacing the free endpart in a direction orthogonal to a lamination direction, wherein:

at least one of the first and second external electrodes is formed on afree end part surface of an outermost layer of the piezoelectricmaterial in the lamination direction so that a part of the piezoelectricmaterial outermost layer, located in the active region, can beactivated;

the part of the piezoelectric material outermost layer, located in theactive region, is used as a trimming portion whose effective range canbe varied by trimming;

an active range of the piezoelectric material outermost layer can bevaried by trimming the trimming portion to adjust the displacementamount of the piezoelectric vibrator.

(32) The piezoelectric vibrator unit of (31), wherein the piezoelectricvibrators are manufactured by

laminating piezoelectric material layers and internal electrode layersalternately to provide a laminate substrate;

forming an external electrode layer on at least a surface of thelaminate substrate to provide a laminate member; and

at least partially cutting the laminate member to provide thepiezoelectric vibrators in the form of teeth of comb.

(33) The piezoelectric vibrator unit of (31) or (32), wherein:

the first internal electrodes are common internal electrodes set to thesame potential level for all the piezoelectric vibrators;

the second internal electrodes are segment internal electrodes whosepotential level is set depending on the respective piezoelectricvibrator;

the first external electrodes are common external electrodes set to thesame potential level for all the piezoelectric vibrators; and

the second external electrodes are segment external electrodes whosepotential level is set depending on the respective piezoelectricvibrator.

(34) The piezoelectric vibrator unit of anyone of (31) to (33), whereineach of the piezoelectric vibrators includes an inactive part which isnot displaced even when the piezoelectric material in the active regionis activated, and the inactive part is joined to a fixing plate.

(35) The piezoelectric vibrator unit of any one of (31) to (34), whereineach of the piezoelectric vibrators includes an inactive part which isnot displaced even when the piezoelectric material in the active regionis activated, and the first and second external electrodes are broughtinto electrically conducted to a wiring member in the inactive part.

(36) The piezoelectric vibrator unit of any one of (31) to (35), whereinthe piezoelectric material outermost layer is thicker than an internallayer of piezoelectric material.

(37) A liquid jet head comprising:

a piezoelectric vibrator unit manufactured according to themanufacturing method of any one of (1) to (26); and

a flow passage unit having a plurality of liquid flow passages that arerespectively associated with the piezoelectric vibrators, and thatrespectively extend from a reservoir through pressure chambers to nozzleopenings, wherein:

the piezoelectric vibrator unit is attached to the flow passage unit sothat the piezoelectric vibrators are respectively contacted withdiaphragm parts of the pressure chambers associated with thepiezoelectric vibrators; and

deformation of the piezoelectric vibrator deforms the associatedpressure chamber and changes liquid pressure to in the associatedpressure chamber to thereby eject liquid from the associated nozzleopening.

(38) A liquid jet head manufactured according to the manufacturingmethod of any one of (27) to (30), the liquid jet head comprising:

a case defining a storage space in which the piezoelectric vibrators canbe stored;

an adjustment opening formed through the case for communication betweenan outside of the case and the storage space to enable access to thepiezoelectric vibrators stored in the storage space, wherein

displacement amount adjustment can be conducted to each of thepiezoelectric vibrator from the outside of the case through theadjustment opening.

(39) The liquid jet head of (38), wherein each of the piezoelectricvibrator includes common internal electrodes and segment internalelectrodes laminated alternately with a layer of the piezoelectricmaterial interposed between adjacent pair of the common and segmentinternal electrodes to form an active region in a free end part.

(40) The liquid jet head of (39), wherein each of the piezoelectricvibrators is displaced in a direction orthogonal to a laminationdirection by the action of an electric field.

(41) The liquid jet head of (39), wherein each of the piezoelectricvibrators is displaced in a lamination direction by the action of anelectric field.

(42) The liquid jet head of any one of (39) to (41), wherein thepiezoelectric vibrators are manufactured by:

laminating piezoelectric material layers and internal electrode layersalternately to provide a laminate substrate;

forming an external electrode layer on at least a surface of thelaminate substrate to provide a laminate member; and

at least partially cutting the laminate member to provide thepiezoelectric vibrators in the form of teeth of comb.

The present disclosure relates to the subject matter contained inJapanese patent application Nos. Hei. 11-371155 (filed on Dec. 27,1999), 2000-17886 (filed on Jan. 24, 2000), and, which are expresslyincorporated herein by reference in their entireties.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a sectional view to show the main part of an ink jet recorderon an enlarged scale;

FIG. 2 is a perspective view of the appearance of a piezoelectricvibrator unit;

FIG. 3 is a sectional view take on line A-A in FIG. 2;

FIG. 4 is a drawing to show the relationship between the effectivelength of an external electrode and displacement amount;

FIG. 5 is a flowchart to describe a displacement amount adjustmentmethod by executing trimming;

FIG. 6 is a flowchart to describe another displacement amount adjustmentmethod by executing trimming;

FIG. 7 is a sectional view to describe another drive vibratorconfiguration;

FIG. 8 is a sectional view to describe still another drive vibratorconfiguration;

FIG. 9 is a flowchart to describe a displacement amount adjustmentmethod based on polarization degree;

FIG. 10 is a flowchart to describe another displacement amountadjustment method based on polarization degree;

FIG. 11 is a sectional view to show the main part of a recording headusing drive vibrators in a horizontal vibration mode on an enlargedscale;

FIG. 12 is a flowchart to describe a displacement amount adjustmentmethod based on pixel size; and

FIG. 13 is a flowchart to describe another displacement amountadjustment method based on pixel size.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the accompanying drawings, preferred embodiments of theinvention will be described. In the following description, an ink jetrecording head is discussed as an example of a liquid jet head. Therecording head is not only used in an image recording apparatus such asa printer and a plotter, but also applicable to industrial machines.

A recording head 1 shown in FIG. 1 includes a case 2, a flow passageunit 3, a piezoelectric vibrator unit 4, etc. For convenience indescribing the recording head 1; the top of FIG. 1 is referred to as aleading end side and the bottom of FIG. 1 is referred to as a base endside.

The case 2 is a block-shaped member made of a synthetic resin, having astorage space 5, the leading end and the rear end of which are bothopen. The flow passage unit 3 is joined to the leading end of the case2, and the piezoelectric vibrator unit 4 is housed in the storage space5 in a state in which the leading ends of comb-shaped teeth of avibrator group 6 is confronted with the leading end side opening of thestorage space 5. An ink supply tube 7, which communicates with an inkcartridge (not shown) on the base end side, is provided to a lateralside of the storage space 5.

The flow passage unit 3 is mainly made up of a flow passage formationplate 10, a nozzle plate 11, and an elastic plate 12.

The nozzle plate 11 is a thin plate-like member provided with aplurality of (for example, 96) nozzle openings 13 . . . arrayed in a rowor rows at pitches corresponding to dot formation density. The nozzleplate 11 is formed, for example, by a stainless plate.

The flow passage formation plate 10 stacked or laminated on the nozzleplate 11 is formed with a reservoir 14 (a common ink chamber) into whichink supplied through the ink supply tube 7 flows, pressure chambers 15each for generating ink pressure required for ejecting ink from acorresponding one of the nozzle openings 13, and ink supply ports 16 forcommunication of the reservoir 14 with the pressure chambers 15. In theembodiment, a silicon wafer is subjected to etching treatment to obtainthe flow passage formation plate 10 having these components.

In the embodiment, the elastic plate 12 has such a double structure thata polymer film, such as PPS (polyphenylene sulfide), is laminated as anelastic film 17 on a support plate 18, such as a stainless plate. Thesupport plate 18 are partially perforated by etching treatment so that acompliance part 19 corresponding to the reservoir 14 and diaphragm parts20 corresponding to the respective pressure chambers 15 are formed onlyby the elastic film 17. Each diaphragm part 20 is formed with an islandpart 21 by removing the support plate 18 annularly so as to leave thecenter portion. The island part 21 has a rear side to which the leadingend surface part of a respective drive vibrator 24 described later isjoined. A plurality of the island parts 21 are provided at pitchescorresponding to the dot formation density similarly to the nozzleopenings 13, and each of the island parts 21 is formed as a block havinga narrow width corresponding to the nozzle array direction and a longerlength corresponding to the laminated direction (described later) in thedrive vibrator 24.

The flow passage unit 3 is manufactured by placing the nozzle plate 11and elastic plate 10 on the front side and the rear side of the flowpassage formation plate 10, respectively to interpose the flow passageformation plate 10 between the nozzle plate 11 and the elastic plate 12,and integrating them together by bonding, etc. The elastic plate 12 ofthe flow passage unit 3 forms a part of a seal member for sealing theceiling surfaces of the pressure chambers 15 and the reservoir 14.Therefore, a set of ink flow passages are defined within the flowpassage unit 3, which correspond in number to the drive vibrators 24 andwhich respectively extend from the reservoir 15 through the pressurechambers 15 to the nozzle openings 13. The ink flow passage correspondsto a liquid flow passage of the invention.

As shown in FIG. 2, the piezoelectric vibrator unit 4 is mainly made upof the vibrator group 6 having a plurality of piezoelectric vibrators 24and 26, and a fixing plate 25 for supporting the vibrator group 6. Thepiezoelectric vibrators are arrayed as a row like teeth of the combshape, and the vibrator group 6 has a pair of dummy vibrators 26 and 26located at both outermost ends in the row (in the array direction), anda plurality of drive vibrators 24 . . . disposed between the dummyvibrators 26 and 26. The drive vibrators 24 are piezoelectric vibratorsassociated with ink droplet ejection, and formed separately one fromanother into needles each having an extremely narrow width of about 50μm to 100 μm, for example. The dummy vibrators 26 are piezoelectricvibrator not associated with the ink droplet ejection, each having asufficiently wider width than the drive vibrator 24 so as to providenecessary rigidity. The drive vibrator 24 in the embodiment is apiezoelectric vibrator of so-called vertical vibration mode, anddisplaced (expanded and contracted) in a direction orthogonal to thelaminating direction of the piezoelectric members and the electrodes, asdescried later.

Next, the drive vibrator 24 will be discussed. As shown in FIG. 3, thedrive vibrator 24 is a laminated-type piezoelectric vibrator in whichcommon internal electrodes 27 (corresponding to first internalelectrodes of the invention) and segment internal electrodes 28(corresponding to second internal electrodes of the invention) arelaminated alternately with piezoelectric material (a layer ofpiezoelectric material) 29 interposed between the adjacent internalelectrodes. The common internal electrodes 27 are electrodes for settingthe same potential level for all drive vibrators 24. The segmentinternal electrodes 28 are electrodes, each for setting a potentiallevel for a respective drive vibrator 24 in response to a supplied drivesignal.

In the embodiment, the portion of the drive vibrator 24 from the leadingend thereof to about a half or two thirds in the vibrator lengthdirection (direction orthogonal to the lamination direction) is a freeend part 24 a. The remaining portion of the drive vibrator 24, namely,the portion from the end of the free end part 24 a to the vibrator baseend is a base end part 24 b.

The free end part 24 a is formed with an active region L where thecommon internal electrodes 27 and the segment internal electrodes 28overlap each other (overlap portion). When a potential difference isgiven to the internal electrodes 27, 28, the piezoelectric material 29in the active region L is activated and deformed so that the free endpart 24 a is displaced (expanded or contracted) in the vibrator lengthdirection. The base ends of the common internal electrodes 27 areelectrically conducted to a common external electrode 30 at the base endsurface part of the drive vibrator 24. On the other hand, the leadingends of the segment internal electrodes 28 are electrically conducted toa segment external electrode 31 at the leading end surface part of thedrive vibrator 24. The leading ends of the common internal electrodes 27are positioned slightly behind the leading end surface part of the drivevibrator 24 so as not to be exposed from the leading end surface part ofthe drive vibrator 24. The base ends of the segment internal electrodes28 are positioned at the boundary between the free end part 24 a and thebase end part 24 b.

The segment external electrode 31 is an electrode formed on the leadingend surface part of the piezoelectric vibrator 24 and a wiringconnection surface (upper surface in FIG. 3) of the piezoelectricvibrator 24, i.e. one side surface in the lamination direction in thepiezoelectric vibrator 24, for electrical connection of the segmentinternal electrodes 28 to a wiring pattern of a flexible cable 32 (akind of wiring member of the invention). The portion of the segmentexternal electrode 31 on the wiring connection surface side is formedcontinuously from leading end surface part to reach the base end part 24b. As shown in FIG. 2, a plurality of segment external electrodes 31 areprovided for respective drive vibrators 24.

The common external electrode 30 is an electrode formed on the base endsurface part of the piezoelectric vibrator 24, the wiring connectionsurface, and a fixing plate attachment surface (lower surface in FIG.3), i.e. the opposite side surface in the lamination direction in thepiezoelectric vibrator 24, for electrical connection of the commoninternal electrodes 27 to the wiring pattern of the flexible cable 32.The portion of the common external electrode 30 on the wiring connectionsurface is formed continuously from a position slightly behind the endpart of the segment external electrode 31 toward the base end surfacepart and the portion of the common external electrode 30 on the fixingplate attachment surface is formed continuously from a position slightlybehind the leading end surface part of the vibrator toward the base endsurface part. As shown in FIG. 2, the common external electrode 30 inthis embodiment continuously extends across the vibrator group 6 in thearray direction at least on the base end surface part of the vibratorgroup 6.

Each of the external electrodes 30 and 31 also functions as anelectrodes for activating the piezoelectric material 29 of the outermostlayer (corresponding to an outermost piezoelectric material of theinvention). That is, the segment external electrode 31 is paired withthe common internal electrode 27 such that piezoelectric material 29 aformed as the outermost surface in the lamination direction isinterposed therebetween, and the common internal electrode 27 and thesegment external electrode 31 overlap each other in the active region L.Therefore, the portion of the piezoelectric material 29 a in the activeregion L becomes deformed due to the potential difference between thecommon internal electrode 27 and the segment external electrode 31.Likewise, the common external electrode 30 is paired with the segmentinternal electrode 28 such that piezoelectric material 29 b formed onthe outermost surface in the lamination direction is interposedtherebetween, and the segment internal electrode 28 and the commonexternal electrode 30 overlap each other in the active region L.Therefore, the portion of the piezoelectric material 29 b in the activeregion L becomes deformed due to the potential difference between thesegment internal electrode 28 and the common external electrode 30. Inshort, in the piezoelectric material 29 a, 29 b, the regions having bothsurfaces directly sandwiched between the electrodes 27, 28, 30, 31become deformed.

In the embodiment, the portion of the common external electrode 30 inthe active region L is used as a trimming portion. An effective length x(range in which the piezoelectric material 29 b is activated) of thistrimming portion is varied by trimming, namely, removing a part of thecommon external electrode 30. For example, if the trimming portion isnot subjected to trimming, the common external electrode 30 having theeffective length x equal to the active region L activates thepiezoelectric material 29 b.

If the part of the common external electrode 30 is removed from aremoval region 33 shown in FIG. 3, the common external electrode 30having the effective length x shorter than the active region L activatesthe piezoelectric material 29 b. This means that the leading end sideportion of the piezoelectric material 29 b ahead of the effective lengthx becomes inactive, and is not associated with expansion or contractionof the drive vibrator 24. Therefore, the active range in thepiezoelectric material 29 b becomes narrow to make the displacementamount of the drive vibrator 24 smaller than that in the state in whichtrimming is not executed.

The displacement amount of the drive vibrator 24 is decreased almostlinearly as indicated by the line of letter D in FIG. 4 as the effectivelength x of the external electrode becomes shorter. Thus, it is seenthat the displacement amount of the drive vibrator 24 can be changed asit is lessened depending on how the effective length x is given. Thenumber of laminated layers of the piezoelectric material 29 normally isabout 20 to 30 although several layers are shown in the figure forsimplifying the illustration. Thus, the displacement amount can bechanged at about several % of the entire displacement amount byadjusting the effective length x of the trimming portion. A specifictrimming procedure will be described later.

The base end part 24 b functions as an inactive part not expanded orcontracted even when the piezoelectric material 29 in the active regionL is activated. The flexible cable 32 is disposed on the wiringconnection surface side of the base end part 24 b, and the segmentexternal electrode 31 and the common external electrode 30 areelectrically connected to the flexible cable 32 on the base end part 24b. That is, each common electrode wiring part 34 and each segmentelectrode wiring part 35 shown in FIG. 2 function as wiring connectionparts 34 and 35 onto which connection end parts of the flexible cable 32are placed onto the wiring connection parts 34 and 35. The flexiblecable 32 is installed in place by soldering, etc. A drive signal issupplied through the flexible cable 32 to each electrode. The fixingplate attachment surface of the base end part 24 b functions as a fixingplate joint part onto which the fixing plate 25 is joined. In short, thedrive vibrators 24 . . . and the dummy vibrators 26 and 26 are joinedonto the fixing plate 25 in a so-called cantilever state.

Next, a manufacturing method of the piezoelectric vibrator unit 4 willbe discussed. In this manufacturing method, first a plate-like laminatemember is manufactured (laminate member manufacturing step).

In this step, in the beginning, a plate-like laminate substrate ismanufactured by laminating the common internal electrodes 27 and thesegment internal electrodes 28 alternately with the piezoelectricmaterial 29 interposed therebetween so that the common internalelectrodes 27 and the segment internal electrodes 28 overlap in theleading end side portion forming the free end part 24 a and that anon-overlapping region where only the common internal electrodes 27exist is formed in the base end side portion forming the base end part24 b (laminating step).

If the laminate substrate is manufactured, a segment external electrode31 is formed continuously on the leading end surface part of thelaminate substrate and the range of the wiring connection surface fromthe leading end thereof to the top of the base end part 24 b, and acommon external electrode 30 is formed continuously on the base endsurface part of the laminate substrate, the range of the wiringconnection surface from the base end thereof to the top of the base endpart 24 b, and the fixing plate attachment surface, therebymanufacturing a laminate member with the external electrodes (externalelectrode formation step).

The laminate member thus manufactured is cut to provide a vibrator group6 having a plurality of piezoelectric vibrators 24 and 26 arrayed in arow (vibrator manufacturing step). In this step, first a fixing plate 25is joined to the fixing plate attachment surface of the base end part 24b of the laminate member by bonding, etc. After the fixing plate 25 isjoined, a wire saw, a dicing saw, etc., is used to cut and divide thelaminate member into teeth of the comb, i.e. into individualpiezoelectric vibrators 24 and 26 in the form of elongated needles, asshown in FIG. 2. At this time, as shown in FIGS. 1 and 2, a slant groove36 is formed so that cutting lines for the laminate member on the fixingplate 25 side extends down to the leading end position of the fixingplate 25 and the cutting lines on the wiring connection surface sideextends down to the base end surface part. The reason why the plate-likelaminate member is joined to the fixing plate 25 before it is dividedinto teeth of comb is to stably divide the laminate member andfacilitate handling during subsequent processing. Therefore, if thelaminate member can be stably divided into teeth of comb, the laminatemember may be joined to the fixing plate 25 after it is divided intoteeth of comb.

In the piezoelectric vibrator unit 4 thus manufactured, each drivevibrator 24 has an extremely narrow width of about 50 μm to 100 μm.Thus, if a defect or a pinhole larger than the width only exists in aninternal electrode, the portion using the internal electrode 27 or 28loses activity and is not displaced. When the internal electrodes 27 and28 are laminated sequentially, an offset of an internal electrode mayoccur. Further, since the mechanical processing method is adopted, thewidths of the drive vibrators 24 may be varied. For these reasons, thereis a possibility that the displacement amount (expansion or contractionamount) of each of the drive vibrators 24 formed like comb teeth mayvary from one drive vibrator 24 to another.

Then, in the embodiment, after the plate-like laminate member is dividedlike comb teeth to provide the piezoelectric vibrators 24 and 26, thedisplacement amounts of the drive vibrators 24 . . . are adjusted to beuniform. In the embodiment, a laser beam is irradiated onto the trimmingportion of the drive vibrator 24 (portion of the common externalelectrode 30 in the active region L) to partially remove the commonexternal electrode 30. With this processing, the displacement amounts ofthe drive vibrators 24 . . . are made identical to the displacementamount of the drive vibrator 24 having the smallest displacement amount.This means that the drive vibrator 24 having the smallest displacementamount is used as a reference vibrator, and the displacement amounts ofother drive vibrators 24 . . . are adjusted to be identical to thedisplacement amount of the reference vibrator. This makes thedisplacement amounts of the drive vibrators 24 . . . uniform.

A displacement amount adjustment method will be discussed with referenceto a flowchart of FIG. 5.

As a first step of the adjustment method, the displacement amounts ofall drive vibrators 24 . . . with respect to reference voltage aremeasured separately (displacement amount measurement step, S1). In thedisplacement amount measurement step, for example, the displacementspeed of each drive vibrator 24 when the reference voltage is suppliedbetween the common electrode (the common external electrode 30, thecommon internal electrodes 27) and the segment electrode (the segmentexternal electrode 31, the segment internal electrodes 28) is measuredusing a laser Doppler vibration meter, etc., and is integrated in thetime direction, thereby calculating the displacement amount. Thedisplacement amount may be measured directly using a laser displacementgage, etc.

The drive vibrator 24 having the smallest displacement amount withrespect to the reference voltage among all drive vibrators 24 . . . isused as the reference vibrator, and the displacement amount of thereference vibrator is set to a target displacement amount (targetvalue).

If the target displacement amount is set, the treatment conditions forthe respective drive vibrators 24 . . . are set based on the measurementresult of the displacement amount measurement step, and displacementamount adjustment is executed based on the setup treatment conditions(displacement amount adjustment step).

In the displacement amount adjustment step, first, the treatmentconditions are set. In the embodiment, the displacement amount of eachdrive vibrator 24 is adjusted by trimming the trimming portion and thusthe trimming amount is set as the treatment condition for each drivevibrator 24. That is, the measured displacement amount of each drivevibrator 24 is obtained, and the difference between the obtaineddisplacement amount and the target displacement amount is calculated(S2). Next, the effective length x of the trimming portion is calculatedfrom the difference between the displacement amount measurement valueand the target displacement amount. This means that what μm the commonexternal electrode 30 is to be trimmed is calculated (S3).

To execute this calculation, for example, table information indicatingthe relationship between the effective length x of the common externalelectrode 30 and the displacement amount as shown in the graph of FIG. 4is previously stored in memory of a microcomputer forming a controller,and is referenced.

If the treatment condition is set, trimming treatment (a kind ofdisplacement amount adjustment) is performed based on the setuptreatment condition. That is, laser beam machining is performed based onthe calculated trimming amount and the trimming portion is trimmed toremove a part of the common external electrode 30 (S4).

If the trimming treatment at step S4 is performed, whether or not anunadjusted drive vibrator 24 exists is determined (S5). If an unadjusteddrive vibrator 24 exists, control returns to step S2 and the treatmentfor the unadjusted drive vibrator 24 is executed in a similar manner. Onthe other hand, if the treatment for all drive vibrators 24 . . .terminates, adjustment to the piezoelectric vibrator unit 4 isterminated.

The piezoelectric vibrator unit 4 manufactured according to thedescribed procedure is disposed so that the leading end surface parts ofthe drive vibrators 24 are contacted with and joined to the rear sidesof the island parts 21 of the diaphragm parts 20, respectively, as shownin FIG. 1. Thus, when a drive signal is supplied to expand or contactthe drive vibrator 24 in the vibrator length direction, the diaphragmpart 20 becomes deformed in the back and forth direction to change thevolume of the pressure chamber 15.

To eject an ink droplet from the nozzle opening 13, a drive signal issupplied selectively to the drive vibrator 24 associated with the inkdroplet ejection so that, for example, the pressure chamber 15 is onceexpanded, then contracted. In doing so, as the pressure chamber 15 isexpanded, ink in the reservoir 14 flows into the pressure chamber 15,and as the pressure chamber 15 is contracted, the ink pressure in thepressure chamber 15 is raised. Ink pushed out from the nozzle opening 13is ejected as an ink droplet.

At this time, in the embodiment, the piezoelectric vibrator unit 4 ismanufactured through the displacement amount measurement step and thedisplacement amount adjustment step, and the displacement amounts of thedrive vibrators 24 are made identical with the displacement amount ofthe reference vibrator, so that the ejection characteristic, such as theink droplet ejection amount, the ejection speed, the dot size (area ofthe ejected ink droplet) onto a print recording medium, such as recordpaper, etc., (namely, the liquid ejection characteristic) can be madeuniform at high level.

Even the piezoelectric vibrator unit 4 which had to be handled as adefective formerly can be mounted to a product by being subjected tothis adjustment, and the manufacturing yield can also be raised.

To set the target displacement amount, the drive vibrator 24 having thesmallest displacement amount with respect to the reference voltage isused as the reference vibrator, and the displacement amounts of otherdrive vibrators 24 . . . are adjusted to be identical to thedisplacement amount of the reference vibrator in the displacement amountadjustment step, but the invention is not limited to this method. Forexample, a displacement amount smaller than the displacement amount ofthe reference vibrator is set as the target displacement amount, and thedisplacement amounts of all drive vibrator 24 including the referencevibrator may be adjusted to be identical to the target displacementamount thus set.

If the displacement amounts of drive vibrators 24 . . . other than thereference vibrator are adjusted to be identical to the displacementamount of the reference vibrator as in the above-described method, thedisplacement amount adjustment can be minimized, and thus conductedefficiently.

In the embodiment, the effective length x of the common externalelectrode 30 is adjusted at the last stage of the manufacturing step ofthe piezoelectric vibrator unit 4. Accordingly, the possibility that thedisplacement amount of each drive vibrator 24 may be changed after theadjustment is low, and adjustment can be made reliably.

To adjust the effective length x, any method may be adopted if a part ofthe common external electrode 30 can be removed. If laser beam machiningis adopted as in the embodiment, a part of the common external electrode30 can be removed easily with good accuracy.

By the displacement amount adjustment of the embodiment, only oneexternal electrode (common external electrode 30) is made partiallyinactive and thus there is a possibility that a bending mode (deflectionmode) may occur when the drive vibrator 24 is displaced. However, sincethe leading end surface part of the drive vibrator 24 is joined to theisland part 21, and the bending mode is restricted and does not appearbecause of bonding to the island part 21. Consequently, only a vibrationmode for expanding and contracting in the vibrator length directionoccurs.

By the way, the above-described adjustment method is a method ofexecuting one trimming treatment for one drive vibrator 24 foradjustment, but the invention is not limited to this adjustment method.For example, plural trimming treatment may be executed for one drivevibrator 24 for adjustment.

Next, this adjustment method will be discussed with reference to aflowchart of FIG. 6. The adjustment method includes a displacementamount measurement step and a displacement amount adjustment stepsimilarly to the adjustment method previously described with referenceto FIG. 5.

That is, in the displacement amount measurement step, the displacementamount of each of the drive vibrators 24 . . . is measured as at step S1in FIG. 5 and the target displacement amount is set (S11). If the targetdisplacement amount is set, the displacement amount of the drivevibrator 24 to be adjusted is obtained and whether or not the obtaineddisplacement amount falls within a predetermined allowable range isdetermined (S12).

If the obtained displacement amount is out of the allowable range, aprogram advances to the displacement amount adjustment step. In thisdisplacement amount adjustment step, first the treatment condition isset. In this method, first a difference between the displacement amountof the drive vibrator 24 to be adjusted and the target displacementamount is calculated and the trimming amount is determined based on thedifference. If the trimming amount is determined, the half value of thedetermined trimming amount is set as an actual trimming amount adoptedfor actually removing a part of the common external electrode 30 (S13).If the treatment condition (actual trimming amount) is thus set, laserbeam machining is performed based on the setup treatment condition forremoving a part of the common external electrode 30 (S14).

If trimming is performed, the displacement amount of the drive vibrator24 to be adjusted is measured (S15) and step S12 is subsequentlyexecuted. At step S12, the displacement amount measured at step S15 iscompared with the target displacement amount and similar treatment tothe above-described treatment is executed.

At step S12, if the displacement amount of the drive vibrator 24 to beadjusted falls within the predetermined allowable range, the adjustmentfor the drive vibrator 24 is terminated and whether or not an unadjusteddrive vibrator 24 exists is determined (S16). If an unadjusted drivevibrator 24 exists, the program returns to step S12 and the treatmentfor the unadjusted drive vibrator 24 is executed in a similar manner. Onthe other hand, if the treatment for all drive vibrators 24 . . .terminates, adjustment to the piezoelectric vibrator unit 4 isterminated.

If the adjustment method as described above is adopted, trimming isexecuted gradually over several times, so that the trimming portion isremoved little by little. Thus, overtrimming can be prevented reliably.

To make the above-described trimming adjustment method more effective,it is preferable that the piezoelectric material 29 a, 29 b of theoutermost layer is made thicker than other piezoelectric material 29.The piezoelectric material 29 a, 29 b of the outermost layer, which isthicker than other piezoelectric material 29, can protect internalelectrodes 27 and 28 if the trimming unintentionally reaches thepiezoelectric material 29 a, 29 b of the outermost layer. This makes itpossible to obtain the piezoelectric vibrator unit 4 which can bereliably mounted to a product. Therefore, the manufacturing yield of thepiezoelectric vibrator unit 4 can be raised.

As shown in FIG. 7, the trimming portion can also be provided using thesegment external electrode 31. A drive vibrator 24A of a modifiedexample is manufactured, for example, according to the followingprocedure: Common internal electrodes 27 and segment internal electrodes28 are laminated alternately with piezoelectric material 29 interposedbetween adjacent electrodes, thereby manufacturing a laminate substrate.The laminate substrate has a non-overlapping region where only thecommon internal electrodes 27 exist.

Note that the non-overlapping region may contain, in addition to theinternal electrodes 27, dummy internal electrodes which are notelectrically connected to the cable 32. This is also applied to theformer embodiment.

In addition, the laminate substrate in the modified example has thecommon internal electrodes 27, 27 as the outermost internal electrodesas shown in FIG. 7.

If the laminate substrate is manufactured, a common external electrode30 is formed continuously in the range from the rear end surface part ofthe laminate substrate to the base end part 24 b on the wiringconnection surface so as to be connected to the common internalelectrodes 27 on the rear end surface part in a direction orthogonal tothe lamination direction of the laminate substrate. A segment externalelectrode 31 is formed continuously from the fixing plate attachmentsurface of the laminate substrate through the leading end surface partto the wiring connection surface so as to be connected to the segmentinternal electrodes 28 on the leading end surface part of the laminatesubstrate. Consequently, a laminate member is manufactured. If thelaminate member is manufactured, a fixing plate 25 is joined to thefixing plate attachment surface of the base end part 25 b in thelaminate member, and the laminate member is cut to have separate teethof comb. The portion of the segment external electrode 31 on the fixingplate attachment surface is used as a trimming portion, and laser beammachining is executed for the trimming portion to partially remove thetrimming portion of the segment external electrode 31. Accordingly, inthe modified example, the displacement amounts of the drive vibrators24A can also be adjusted to be uniform.

By the way, in the first embodiment, the trimming treatment is executedduring the process of manufacturing the piezoelectric vibrator unit 4.The invention is not limited to this exemplified method. For example,the displacement amount adjustment (trimming treatment) may be executedafter the vibrator unit, obtained by cutting the laminate member to haveteeth of comb, is fixedly stored in the storage space 5 of the case 2. Asecond embodiment of the invention adopting this method will bediscussed.

In the second embodiment, an adjustment opening 37 for communicationbetween the outside of the case 2 and the storage space 5 is formedthrough the case 2, as indicated by one-dotted chain line in FIG. 1. Theadjustment opening 37 is provided for executing the displacement amountadjustment for the drive vibrators 24 . . . from the outside of the case2, and is confronted with the trimming portions of the drive vibrators24 . . . .

Therefore, a laser beam is applied to each trimming portion through theadjustment opening 37, whereby the displacement amount of each drivevibrator 24 can be adjusted with the piezoelectric vibrator unit 4 builtin the recording head 1.

A manufacturing method of recording head 1 according to the secondembodiment will be discussed briefly.

In the manufacturing method, first a piezoelectric vibrator unit 4 ismanufactured. A plate-like laminate member is manufactured as in thefirst embodiment. That is, the common internal electrodes 27 and thesegment internal electrodes 28 are laminated alternately with thepiezoelectric material 29 interposed between adjacent internalelectrodes so that the active region is formed in the free end part 24a, thereby manufacturing a plate-like laminate substrate. A segmentexternal electrode 31 and a common external electrode 30 are formed onthe surface or surfaces of the laminate substrate, thereby manufacturinga laminate member provided with the external electrodes. If the laminatemember is manufactured, a fixing plate 25 is joined to the fixing plateattachment surface of the laminate member, and the laminate member iscut to have teeth of comb teeth, i.e. a plurality of the piezoelectricvibrators 24 and 26.

If the piezoelectric vibrator unit 4 is manufactured, a case 2 and aflow passage unit 3 separately manufactured are joined to each other,and the piezoelectric vibrator unit 4 is accommodated in the interior ofthe joint assembly, i.e. within the storage space 5.

If the piezoelectric vibrator unit 4 is accommodated within the storagespace 5, the liquid ejection characteristics of nozzle openings 13 . . .are adjusted. This adjustment method includes an ejection characteristicmeasurement step and an ejection characteristic adjustment step.

The ejection characteristic measurement step is a step at which the samedrive signal is applied to all drive vibrators 24 . . . to eject the inkdroplet from the nozzle openings 13 . . . , and the ink droplet ejectioncharacteristic (a kind of liquid ejection characteristic) is measuredfor each of the nozzle openings 13 . . . . In the embodiment, the inkdroplet ejection amount (namely, the liquid ejection amount) is measuredas the ink ejection characteristic. For example, ink droplets areejected repeatedly the stipulated number of times of about 10,000 to100,000 from one nozzle opening 13 and the ink droplet ejection amountis calculated based on the difference between the weight before inkdroplet ejection and that after ink droplet ejection. For example, theejected ink droplets may be collected and their weight may be measured,or the ink droplet ejection amount may be obtained from the differencebetween the weight of the ink cartridge before and after the ink dropletejection.

The ejection characteristic adjustment step is a step at which theliquid ejection characteristics of the nozzle openings 13 . . . are madeuniform. In the embodiment, trimming treatment (a kind of displacementamount adjustment) is performed for the drive vibrators 24, therebymaking the ejection characteristics uniform. That is, the treatmentcondition for each drive vibrator 24 is set based on the result ofmeasurement by the ejection characteristic measurement step, and thetrimming amount for the trimming portion is set based on the setuptreatment condition. If the trimming amount is set, laser beam machiningis executed for trimming the trimming portion to remove a part of thecommon external electrode 30. In this case, the drive vibrator 24 havingthe smallest ink droplet ejection amount is used as a referencevibrator, and the adjustment is conducted so that the displacementamounts of other drive vibrators 24 . . . are decreased, thereby makingthe ink droplet ejection amounts uniform.

If the adjustment method as described above is adopted, the displacementamount of each drive vibrator 24 is adjusted based on the ink amountactually ejected. Accordingly, the variation in ink ejection amount,which is caused by other factors than the drive vibrators 24, can becorrected by this adjustment. For example, the variation in ink ejectionamount, caused by varying joint state of the drive vibrator 24 to theisland part 21, varying size of the nozzle opening 13, varying shape ofthe pressure chamber 15, etc., can be all corrected by this adjustment.Since the displacement amount adjustment is carried out at the laststage of the manufacturing step of the recording head 1, any additional,wasteful steps, such as re-adjustment can be dispensed with.Accordingly, the manufacturing of the recording head 1 can be madeefficient.

In the second embodiment, the liquid ejection characteristic is notlimited to the ink droplet ejection amount. For example, it may be theink droplet ejection speed (namely, liquid ejection speed) or may be thesize of a pixel (namely, the area of the ejected ink droplet) on aprinting or recording medium obtained as an ink droplet is ejected ontothe printing or recording medium. If any of them is selected as theliquid ejection characteristic, a similar advantage can be provided.

Although each of the above-described embodiments executes trimming ofthe trimming portions to adjust the displacement amounts of the drivevibrators 24 (24A), thereby making the ink droplet ejection amountsuniform, the invention is not limited thereto or thereby. For example,the polarization state of piezoelectric material 29 forming a part ofthe drive vibrator can also be adjusted for adjusting the displacementamount. A third embodiment of the invention wherein the polarizationstate is adjusted will be discussed.

The third embodiment slightly differs in piezoelectric vibratorconfiguration from the above-described embodiments. That is, as shown inFIG. 8, a drive vibrator 24B of the third embodiment has no trimmingportion, and the surface, corresponding in location to the trimmingportion, is covered with the external electrode. Other parts of thethird embodiment are similar to those of the first and secondembodiments, and therefore identical parts are denoted by the samereference numerals and will not be discussed again.

The embodiment is featured by a manufacturing method. This manufacturingmethod will be discussed in detail.

In this manufacturing method, first a plate-like laminate substrate ismanufactured (laminating step). In this laminating step, an electrodelayer 27, 28 is formed between adjacent layers of a large number oflaminated piezoelectric material 29 . . . . Particularly, the commoninternal electrodes 27 and the segment internal electrodes 28 arelaminated alternately with the piezoelectric material 29 interposedbetween adjacent internal electrodes, thereby manufacturing a laminatesubstrate. The common internal electrode 27 and the segment internalelectrode 28 overlap to form an active region L located in the sideforming a free end part 24 a, and only the common internal electrodes 27overlap to form an inactive region or non-overlapping region in the sideforming a base end part 24 b. That is, no active region is formed in thebase end part 24 b side.

Next, the laminate substrate is formed with external electrodes, therebyproviding a laminate member (external electrode formation step). Thatis, the segment external electrode 31 is formed to present an inverted Lshape extending from the leading end surface part, i.e. the free endpart 24 a side of the manufactured laminate substrate, to the laminationsurface forming the wiring connection surface. The common externalelectrode 30 is formed to extend from the base end surface part of thelaminate substrate to both surfaces of the lamination top and bottomsurfaces. Consequently, a laminate member provided with the externalelectrodes is manufactured.

If the laminate member with the external electrodes is manufactured, thelaminate member is cut to manufacture a vibrator group 6 having aplurality of piezoelectric vibrators 24B and 26 arrayed in a row(vibrator manufacturing step). In this step, a wire saw, a dicing saw,etc., is used to divide the free end part 24 a side of the laminatemember joined to the fixing plate 25 into needle-shaped segments eachhaving an extremely narrow width of about 50 μm to 100 μm.

The piezoelectric vibrator unit 4 thus manufactured may have variationin displacement characteristic of the drive vibrators 24B as discussedwith reference to the piezoelectric vibrator unit 4 of the firstembodiment.

Accordingly, also in the third embodiment, the displacement amounts ofthe drive vibrators 24B . . . are made uniform after the plate-likelaminate member is cut to have teeth of comb. In this method,re-polarization treatment is executed, by which the piezoelectricmaterial 29 of semi-saturation polarization state is re-polarized in aforward direction so that the displacement amounts of the drivevibrators 24B . . . are made identical to the drive vibrator 24B havingthe largest displacement amount. That is, the drive vibrator 24B havingthe largest displacement amount is used as a reference vibrator, and thedisplacement amounts of other drive vibrators 24B . . . are adjusted tobe identical to the displacement amount of the reference vibrator.

A displacement amount adjustment method will be discussed with referenceto a flowchart of FIG. 9.

In this adjustment method, first, semi-saturation polarization treatment(S21) is executed for all drive vibrators 24B . . . , such that thedrive vibrators 24B . . . are subjected to the polarization treatmentbut the polarization treatment is terminated before the piezoelectricmaterial 29 is completely polarized, thereby putting the piezoelectricmaterial 29 in a semi-saturation polarization state. In the embodiment,forward polarization voltage, i.e. voltage in the same direction as thevibrators are displaced, is applied to all drive vibrators 24B . . .until the piezoelectric material 29 is put into the polarization stateof 90% of the saturation polarization state. Therefore, in thesemi-saturation polarization treatment, a DC electric field is appliedto the piezoelectric material 29 over a predetermined time.

The term “polarization state of 90% of the saturation polarizationstate” means the polarization state falling within the allowable rangefrom a reference state, provided that the reference state is consideredas 90% of the saturation (100%) polarization state. For example, thepolarization state in the range of ±5% from the 90% polarization state(namely, 85% to 95%) is included in this term. If the semi-saturationpolarization state is thus set, the remaining 10% can be assigned as theadjustment range (margin) in re-polarization treatment (S26) describedlater, so that necessary and sufficient adjustment can be made.

The higher the polarization treatment voltage value, the higher thepolarization degree per unit time, and the longer the voltage applyingtime, the higher the polarization degree. Further, the higher thetemperature of the drive vibrator 24B, the easier polarization. Thus,the voltage value, the voltage applying time, the vibrator temperature,and the like at the polarization treatment time are used as variables,the values are adjusted, and polarization treatment is executed, wherebythe piezoelectric material 29 can be adjusted efficiently to any desiredsemi-saturation polarization state.

If the semi-saturation polarization treatment is executed, then adisplacement amount measurement step (S22) is started. In thisdisplacement amount measurement step, the displacement amounts of drivevibrators 24B . . . with respect to the reference voltage are measuredseparately. In the displacement amount measurement step, for example,the displacement speed of each drive vibrator 24B when the referencevoltage is supplied is measured using a laser Doppler vibration meter,etc., and is integrated in the time direction, thereby calculating thedisplacement amount. The displacement amount may be measured directlyusing a laser displacement gage, etc.

If the displacement amounts of drive vibrators 24B . . . are measured,the target displacement amount is set (S23). Here, the target value ofthe displacement amount applied to all drive vibrators 24B . . . is set.Since each of the drive vibrators 24B . . . has a polarization margin ofabout 10% in the forward direction as described above, for example, thedrive vibrator 24B having the maximum displacement amount is used as areference vibrator, and the displacement amount of the referencevibrator is set as the target displacement amount.

The maximum displacement amount of the drive vibrator 24B is adopted asthe target displacement amount, but the invention is not limitedthereto. For example, the displacement amount larger than thedisplacement amount of the reference vibrator is set as the targetdisplacement amount, and the displacement amount of each drive vibrator24B may be adjusted to be identical to the target displacement amount.If the displacement amounts of other drive vibrators 24B . . . than thereference vibrator are adjusted to be identical to the displacementamount of the reference vibrator, the displacement amount adjustment canbe minimized, thus resulting in good efficiency. If the displacementamount larger than the displacement amount of the reference vibrator isadopted as the target displacement amount, the displacement amount ofeach drive vibrator 24B can be set large.

If the target displacement amount is set, the treatment condition foreach of the drive vibrators 24B . . . is set based on the measurementresult by the displacement amount measurement step, and displacementamount adjustment is executed based on the setup treatment condition(displacement amount adjustment step) In the displacement amountadjustment step, first the treatment condition is set. In theembodiment, the displacement amount of each drive vibrator 24B isadjusted according to the polarization degree, and thus there-polarization treatment condition is set as the treatment condition.

That is, a determination step (S24) is executed, which calculates thedifference between the displacement amount of the drive vibrator 24B tobe adjusted and the target displacement amount, and determines whetheror not the difference falls within the allowable range. In thedetermination step, if the difference between the displacement amountand the target displacement amount is outside the allowable range, theprogram returns to a treatment condition setting step (S25) to adjustthe corresponding drive vibrator 24B. If the difference between thedisplacement amount and the target displacement amount falls within theallowable range for all drive vibrators 24B . . . , the process isterminated.

The treatment condition setting step (S25) is a step for setting there-polarization treatment conditions of the drive vibrator 24B to beadjusted based on the difference between the displacement amounts andthe target displacement amount. This means that the re-polarizationtreatment parameters are set for the drive vibrator 24B to be adjusted.Here, the voltage value applied to the piezoelectric material 29, theapplying time of voltage applied to the piezoelectric material 29, andthe temperature of the piezoelectric material 29 are selectedappropriately as the re-polarization treatment parameters (variables)for setting the re-polarization conditions.

The re-polarization treatment conditions may be set so that the drivevibrator of the resultant polarization state exhibit a displacementamount less than the target displacement amount. For example, usingparameters obtained by multiplying by a coefficient of ½, thepolarization state of the drive vibrator 24B may be gradually convergedto the target polarization state providing the target displacementamount as the re-polarization treatment is repeated.

If the re-polarization treatment conditions are set, a re-polarizationtreatment step (a kind of displacement amount adjustment step, S26) isexecuted. In this re-polarization treatment, the voltage value appliedto the piezoelectric material 29, the applying time of voltage appliedto the piezoelectric material 29, the temperature of the piezoelectricmaterial 29, and the like are set appropriately based on there-polarization conditions set at the treatment condition setting step,and the re-polarization treatment is executed under the setupconditions.

After the re-polarization treatment is executed, control returns to theabove-described displacement amount measurement step (S22), and thedisplacement amount of the drive vibrator 24B after the re-polarizationis measured. If the displacement amount is measured, the targetdisplacement amount setting step (S23) is skipped, and the differencebetween the measured displacement amount and the target displacementamount is determined, and if the difference falls within thepredetermined allowable range, another drive vibrator 24B is adjusted.

According to the adjustment method, all drive vibrators 24B . . .(piezoelectric material 29) are put into the semi-saturationpolarization state at the semi-saturation polarization step, and thepiezoelectric material 29 of necessary drive vibrators 24B in thesemi-saturation polarization state is again polarized in the forwarddirection to be adjusted into any desired polarization state. Since thepolarization state is one direction to the saturation side, thepiezoelectric material 29 can be easily adjusted into any desiredpolarization state.

Therefore, the displacement amounts of the drive vibrators 24B . . . aremade uniform. Since the adjustment method is not an adjustment method ofapplying voltage in opposite polarity for inverting the polarization,the reliability of the adjustment is high and the adjustment is easy.

In the third embodiment, the example in which the piezoelectric material29 of the drive vibrators 24B . . . is put into the semi-saturationpolarization state and again polarized in the forward direction to haveany desired identical polarization characteristic, has been described.However, the adjustment method of the third embodiment is not limited tothis example. For example, the piezoelectric material 29 of the drivevibrators 24B . . . may be once put in the complete saturationpolarization state and the drive vibrators 24B . . . in the completesaturation polarization state may be partially heated so that thepiezoelectric material 29 is depolarized partially, thereby adjustingthe displacement amounts of the drive vibrators 24B . . . as desired. Amodified example of the third embodiment adopting such adjustment methodwill be discussed.

FIG. 10 is a flowchart for describing the adjustment method in themodified example. The configuration of recording head 1 and themanufacturing method other than the adjustment method are the same asthose in the third embodiment and therefore will not be discussed again.

In the illustrated adjustment method, first a saturation polarizationtreatment step (S31) is executed. In the saturation polarizationtreatment step, all drive vibrators 24B . . . are polarized to completesaturation, and thus the piezoelectric material 29 is put into thecomplete saturation polarization state. That is, polarization voltage isapplied between segment external electrodes 31 and common externalelectrodes 30 of all drive vibrators 24B . . . to apply a DC electricfield to the piezoelectric material 29 until polarization is saturated.

Next, a displacement amount measurement step (S32) of measuring thedisplacement amounts of the drive vibrators 24B . . . in the saturationpolarization state is executed. In the displacement amount measurementstep, for example, a laser Doppler vibration meter, a laser displacementgage, etc., is used to measure the displacement amount of each drivevibrator 24B when the reference voltage is supplied, as in the thirdembodiment.

Next, a target displacement amount setting step (S33) is executed. Here,the target value of the displacement amount applicable to all drivevibrators 24B . . . is set based on the measurement data obtained by themeasurement step. Since polarization of each drive vibrator 24B . . . issaturated, for example, the drive vibrator 24B having the minimumdisplacement amount is used as a reference vibrator, and thedisplacement amount of the reference vibrator is set as the targetdisplacement amount.

If the target displacement amount is set, the treatment condition foreach of the drive vibrators 24B . . . is set based on the measurementresult at the displacement amount measurement step, and displacementamount adjustment is executed based on the setup treatment condition(displacement amount adjustment step). In the displacement amountadjustment step, first the treatment condition is set. In the modifiedexample, the piezoelectric material 29 is partially depolarized byexecuting spot heating of the drive vibrator 24B so as to adjust thedisplacement amount of the drive vibrator 24B, and thus the spot heatingcondition is set as the treatment condition.

Therefore, first a determination step (S34) of calculating thedifference between the displacement amount of the drive vibrator 24B tobe adjusted and the target displacement amount, and determining whetheror not the difference falls within the allowable range is executed. Inthe determination step, if the difference between the displacementamount and the target displacement amount is outside the allowablerange, a treatment condition setting step (S35) is executed to adjustthe corresponding drive vibrator 24B. If the difference between thedisplacement amount and the target displacement amount falls within theallowable range for all drive vibrators 24B . . . , the process isterminated.

The treatment condition setting step (S35) is a step for setting thespot heating condition for the drive vibrator 24B to be adjusted basedon the difference between the displacement amount and the targetdisplacement amount. This means that the heating condition for the drivevibrator 24B to be adjusted is set. Here, the spot heating area, thespot heating temperature, the spot heating time, and the like are set asthe heating condition. The heating temperature is set to the temperatureat which the piezoelectric material 29 is depolarized, preferably to thetemperature equal to or higher than the Curie temperature of thepiezoelectric material 29.

If the spot heating condition is set, a spot heating step (a kind ofdisplacement amount adjustment step, S36) is executed. In this spotheating step, for example, a laser beam is applied locally to thepiezoelectric material 29 based on the setup heating condition. Theportion of the piezoelectric material 29 where the laser beam isirradiated is locally depolarized thermally, and the displacement amountof the drive vibrator 24B is decreased accordingly. In the spot heatingstep, local irradiation with infrared rays or local abutment of aheating terminal may be performed in place of the laser beamirradiation.

Upon completion of the spot heating step, control returns to thedisplacement amount measurement step (S32), and the displacement amountof the drive vibrator 24B after the spot heating is measured. If thedisplacement amount is measured, the target displacement amount settingstep (S33) is skipped, and the difference between the measureddisplacement amount and the target displacement amount is determined(S34), and if the difference falls within the allowable range, anotherdrive vibrator 24B is adjusted.

According to the adjustment method, all drive vibrators 24B . . .(piezoelectric material 29) are put into the saturation polarizationstate at the saturation polarization step, and the piezoelectricmaterial 29 in the saturation polarization state is locally heated inthe spot heating step for depolarizing the corresponding portion. Thus,the piezoelectric material 29 can be adjusted into any desiredpolarization state by performing simple operation of only heating.Therefore, the displacement amounts of the drive vibrators 24B . . . areeasily made uniform.

The above-described re-polarization adjustment method and the spotheating adjustment method can also be used in combination.

In the modified example, first, in the semi-saturation polarization step(S21), polarization is stopped before saturation, and the piezoelectricmaterial 29 of the piezoelectric vibrators 24B are put into thesemi-saturation polarization state. Next, the displacement amounts ofthe drive vibrators 24B . . . are measured (S22), and the targetdisplacement amount is set based on the measurement value (S23). If thetarget displacement amount is set, the difference between thedisplacement amount of the drive vibrator 24B to be adjusted and thetarget displacement amount is determined (S24), and the treatmentconditions are set (S25, S35). In the condition setting step, if thedisplacement amount is less than the target displacement amount, thecondition for re-polarizing the piezoelectric material 29 in the forwarddirection is set (S25). On the other hand, if the displacement amount isgreater than the target displacement amount, the condition for spotheating the piezoelectric material 29 is set (S35). If the condition isset, a polarization adjustment step (a kind of displacement amountadjustment step) is executed. That is, the re-polarization treatmentstep (S26) or the spot heating step (S36) is selected based on the setupcondition, and is executed. With this adjustment method, thedisplacement amount of drive vibrator 24B can be converged to the targetdisplacement amount efficiently.

In the polarization treatment of the semi-saturation polarization step,the re-polarization step, and the saturation polarization step, thepiezoelectric material 29 can be easily polarized in the forwarddirection (saturation direction) by heating the drive vibrator 24B.Since the piezoelectric material 29 forming a part of the drive vibrator24B has a large dielectric loss, the temperature can be easily raised toabout 100 degrees by vibrating the piezoelectric material 29 in the airat high speed.

Then, in the polarization treatment step (S21, S26, S31), before thepolarization voltage is applied, a polarization drive signal forcharging and discharging the piezoelectric material 29 alternately maybe supplied to the drive vibrator 24B to be adjusted in order to raisethe temperature of the drive vibrator 24B to a predetermined temperatureor higher. According to this heating polarization treatment, the heatgenerated by the drive vibrator 24B itself makes it possible to executeefficient polarization in the polarization step following the heatgeneration.

If the heating polarization treatment is executed, the heatingtemperature, the temperature raising speed, etc., of the drive vibrator24B can be controlled by appropriately setting the waveform of thepolarization drive signal, namely, the crest value and the repetitioncycle. Thus, the method is easy and a special heater, etc., is notrequired.

In the third embodiment and its modified example wherein thepolarization degree is varied for adjusting the displacement amount ofthe drive vibrator 24B, the drive vibrator 24B is a piezoelectricvibrator in the so-called vertical vibration mode and is expanded andcontracted in the direction orthogonal to the lamination direction ofthe piezoelectric material 29 by the action of an electric field.However, the adjustment method can also be applied to a piezoelectricvibrator in so-called horizontal vibration mode expanded and contractedin the lamination direction of piezoelectric material 29 by the actionof an electric field. A modified example will be discussed.

In this modified example, a piezoelectric vibrator unit 4A in thehorizontal vibration mode is used to form a part of a recording head 1,as shown in FIG. 11. This means that the recording head 1 has thepiezoelectric vibrator unit 4A housed in the storage space 5 of the case2. Drive vibrators 24C of the piezoelectric vibrator unit 4A causepressure change of pressure chambers 15 . . . in a flow passage unit 3for ejecting ink droplets from nozzle openings 13 . . . , respectively.Components identical or similar to those previously described withreference to the accompanying drawings are denoted by the same referencenumerals in FIG. 11, and will not be discussed again.

The piezoelectric vibrator unit 4A is mainly made up of a vibrator group6′, a fixing plate 25′, etc. The vibrator group 6′ is formed such thatpiezoelectric material 29 and electrode layers (common internalelectrodes 27, segment internal electrodes 28) are alternately laminatedto provide a laminate substrate, external electrode 30, 31 are formed onthe surfaces of the laminate substrate to provide a laminate member, andlaminate member is cut to have separate teeth of comb with slits atpredetermined pitches corresponding to the pressure chambers 15 . . .defined in the flow passage unit 3.

The vibrator group 6′ differs from the above-described vibrator group 6in shape and placement direction, and the surface of the lamination sideis joined to the fixing plate 25′. The common external electrode 30 andthe segment external electrode 31 are disposed on the opposed sides ofthe drive electrode 24C. In the piezoelectric vibrator unit 4A, thesurface of the piezoelectric material 29 at the leading end becomes theleading end surface part of the corresponding drive vibrator 24A, andthe leading end surface part is jointed to the corresponding island part21 of an elastic plate 12.

A potential difference is given between the opposed internal electrodes27 and 28 to displace (expands or contracts) the corresponding drivevibrator 24C in the lamination direction of the piezoelectric material29 to thereby displace the corresponding diaphragm part 20 partitioningthe corresponding pressure chamber 15. As the diaphragm part 20 isdisplaced, the pressure chamber 15 is expanded or contracted, andpressure change occurs in ink in the pressure chamber 15 for ejecting anink droplet from the corresponding nozzle opening 13.

In the third embodiment wherein the polarization degree of eachpiezoelectric material 29 is adjusted, the polarization degree isadjusted based on the displacement amount of the drive vibrator 24B(24C), but the invention is not limited to the method. For example,polarization degree adjustment (displacement amount adjustment) may beapplied to the assembled recording head 1.

A fourth embodiment adopting this method will be discussed.

Also in a manufacturing method of the fourth embodiment, first apiezoelectric vibrator unit 4 is manufactured as in the secondembodiment described above. That is, the common internal electrodes 27and the segment internal electrodes 28 are laminated alternately withthe piezoelectric material 29 interposed between adjacent internalelectrodes so that the active region is formed in the free end part 24a, thereby manufacturing a plate-like laminate substrate. The segmentexternal electrode 31 and the common external electrode 30 are formed onthe surface of the laminate substrate, thereby manufacturing a Laminatemember provided with the external electrodes. If the laminate member ismanufactured, the fixing plate 25 is joined to the fixing plateattachment surface of the laminate member, and the laminate member iscut to have teeth of comb, i.e. the plurality of piezoelectric vibrators24B and 26.

If the piezoelectric vibrator unit 4 is manufactured, the case 2 and theflow passage unit 3 separately manufactured are joined to each other,and the piezoelectric vibrator unit 4 is housed inside the jointassembly, i.e. within the storage space 5.

If the piezoelectric vibrator unit 4 is housed within the storage space5, the liquid ejection characteristics of nozzle openings 13 . . . areadjusted. This adjustment method is executed according to a procedureshown in a flowchart of FIG. 12, which includes an ejectioncharacteristic measurement step and an ejection characteristicadjustment step.

The ejection characteristic measurement step, like that in the secondembodiment, is a step at which the ink droplet ejection characteristicis measured for each of the nozzle openings 13 . . . . In the fourthembodiment, the size of each pixel formed as a consequence of ejectingan ink droplet onto a printing or recording medium (namely, the area ofthe ejected ink droplet) is measured as the ink ejection characteristic.

Prior to the measurement, first a semi-saturation polarization step(S41) is executed. This means that a DC electric field is appropriatelyapplied to all drive vibrators 24B for polarizing all drive vibrator 24Bto a semi-saturation state.

If the drive vibrators 24B are polarized to the semi-saturation state, apixel measurement step (S42) is executed. In this pixel measurementstep, first, the same drive signal is applied to all drive vibrators 24B. . . for ejecting ink droplets from the nozzle openings 13, therebyforming pixels on a printing or recording medium. If the pixels areformed, then the size of each pixel, namely, the area of ejected ink onthe printing or recording medium is measured.

If each pixel size is measured, the ejection characteristic adjustmentstep is executed. In this ejection characteristic adjustment step,first, a target value setting step (S43) is executed so that the targetvalue of the pixel size applicable to all drive vibrators 24B . . . isset. since this manufacturing method adopts re-polarization foradjusting the displacement amount of the drive vibrator 24B, the size ofthe largest pixel is set to the target value (ejection characteristic),and the displacement amounts of other drive vibrators 24B are adjusted,so that the size of each pixel is adjusted to be identical to thelargest pixel size.

If the target value is set, a determination step (S44) is executed.Whether or not the difference between the size of the pixel recordedusing the drive vibrator 24B to be adjusted and the largest pixel sizefalls within a predetermined allowable range is determined. If thedifference is within the allowable range, the adjustment to the drivevibrator 24B is terminated, and whether or not adjustment to anotherdrive vibrator 24B is to be executed is determined.

If it is determined at the determination step that the difference isoutside the allowable range, a treatment condition setting step (S45) isexecuted, and condition in a re-polarization step (a kind ofdisplacement amount adjustment step, S46) is set. Here, the voltagevalue applied to the piezoelectric material 29, the applying time ofvoltage applied to the piezoelectric material 29, and the temperature ofthe piezoelectric material 29 are selected appropriately as there-polarization treatment parameters (variables) for setting there-polarization condition so that the pixel size becomes the targetvalue.

If the condition is set, a re-polarization step (S46) is executed sothat the piezoelectric material 29 is again polarized in the forwarddirection based on the setup condition.

If the re-polarization step is executed, control returns to the pixelmeasurement step (S42) and the size of the pixel formed using thepiezoelectric vibrator 24B after undergoing the re-polarization ismeasured. If the pixel size is measured, the target value setting step(S43) is skipped, and the above-described steps are executedrepeatingly. If the difference between the measured pixel size and thetarget value falls within the predetermined allowable range, theadjustment to the drive vibrator 24B is terminated, and whether or notadjustment to another drive vibrator 24B is to be executed is determined(S44).

According to this adjustment method, the polarization state of the drivevibrator 24B is adjusted based on the actual size of pixel formed by theejected ink droplet. Therefore, variation in ink ejectioncharacteristic, which is caused not only by varying displacement amountof the drive vibrator 24B but also by varying size of the nozzle opening13, varying shape of the pressure chamber 15, etc., can be correctedtotally. That is, adjustment can be executed in the operating state ofthe recording head 1, and the characteristic of the ink droplet ejectedfrom the nozzle openings 13 . . . can be made uniform at a remarkablyhigh level.

Since the displacement amounts are adjusted at the last stage of themanufacturing step of the recording head 1, there is no risk that thedisplacement amount of each drive vibrator 24B may be changed after theadjustment. Therefore, any additional, wasteful steps, such asre-adjustment, etc., can be dispensed with, and the manufacturing can bemade efficient.

The adjustment method of the fourth embodiment is to execute there-polarization step for adjusting the polarization degree of eachpiezoelectric material 29, but the spot heating may be executed foradjusting the polarization degree. In this case, preferably anadjustment opening for communication between the storage space 5 and theoutside of the case 2 is formed through the case 2, for example, asshown in FIG. 11. The adjustment opening enables a vibrator group 6′housed in the storage space 5 to be accessed from the outside of thecase 2, and the spot heating of each drive vibrator 24C can be executedthrough the adjustment opening. A modified example of the fourthembodiment adopting this method will be discussed.

Also in an adjustment method of the modified example, a piezoelectricvibrator unit 4 is manufactured as in the fourth embodiment. Next, aflow passage unit 3 and a case 2 separately manufactured are joined toeach other, and the piezoelectric vibrator unit 4 is fixedly housed in astorage space 5.

If the piezoelectric vibrator unit 4 is fixedly housed in the storagespace 5, the liquid ejection characteristics of nozzle openings 13 . . .are adjusted. This adjustment method includes an ejection characteristicmeasurement step and an ejection characteristic adjustment step.

In the ejection characteristic measurement step, first, a saturationpolarization step (S51) is executed. This means that a DC electric fieldis applied to all drive vibrators 24C for polarizing all drive vibrators24C to a saturation state. If the drive vibrators 24C are polarized tothe saturation state, a pixel measurement step (S52) is executed. Thispixel measurement step is executed in a similar manner to that at stepS42 described above. That is, first, the drive signal of the samewaveform is applied to all drive vibrator 24C . . . for ejecting inkdroplets from the respective nozzle opening 13, thereby forming pixelson a printing or recording medium. Next, the size of each pixel, namely,the area of ink ejected onto the printing or recording medium ismeasured.

If each pixel size is measured, a target value setting step (S53) isexecuted so that the target value of the pixel size applicable to alldrive vibrators 24C . . . is set. Since this method adopts the spotheating for adjusting the polarization degree, the size of the smallestpixel is set to the target value (ejection characteristic), thedisplacement amounts of other drive vibrators 24C . . . are adjusted sothat the size of each pixel is made identical to the smallest pixelsize.

If the target value is set, a determination step (S54) is executed.Whether or not the difference between the size of the pixel recordedusing the drive vibrator 24C to be adjusted and the smallest pixel sizeis within a predetermined allowable range is determined. If thedifference is within the allowable range, the adjustment to the drivevibrator 24C is terminated and whether or not adjustment to anotherdrive vibrator 24C is to be executed is determined.

If it is determined at the determination step that the difference isoutside the allowable range, a treatment condition setting step (S55) isexecuted so that condition in a spot heating step (a kind ofdisplacement amount adjustment step, S56) is set. Here, the spot heatingarea, the spot heating temperature, the spot heating time, and the likeare set as the heating conditions for adjusting the pixel size to beidentical to the target value.

If the condition is set, a spot heating step (depolarization step, S56)is executed for the drive vibrator 24C to be adjusted. In this spotheating step, for example, a laser beam or infrared ray is locallyapplied to piezoelectric material 29 or a heating terminal is abuttedagainst the piezoelectric material 29, from the outside of the case 2through the adjustment opening. The heated portion is depolarized, andthe displacement amount of the drive vibrator 24C is decreasedaccordingly.

After the spot heating step is executed, control returns to the pixelmeasurement step (S52), and the size of the pixel formed using thepiezoelectric vibrator 24C after undergoing the spot heating ismeasured. If the pixel size is measured, the target value setting step(S53) is skipped, and whether or not the difference between the measuredpixel size and the target displacement amount is within thepredetermined allowable range is determined. If the difference is withinthe predetermined allowable range, adjustment to another drive vibrator24C is executed.

Also in the adjustment method, the polarization state of the drivevibrator 24C is adjusted based on the actual size of pixel formed by theejected ink droplet. Accordingly, the variation in ejectioncharacteristic, which is caused not only by varying displacement amountof the drive vibrator 24C but also by varying size of the nozzle opening13, varying shape of the pressure chamber 15, etc., can be correctedtotally. That is, adjustment can be executed in the operating state ofthe recording head 1, and the characteristic of the ink droplets ejectedfrom the nozzle openings 13 . . . can be made uniform at a remarkablyhigh level.

Since the displacement amounts are adjusted at the last stage of themanufacturing step, there is few possibility that the displacementamount of each drive vibrator 24C may be changed after the adjustment.Therefore, any additional, wasteful steps, such as re-adjustment, etc.,can be dispensed with, and manufacturing can be made efficient.

At the pixel measurement steps (S42 and S52) described above, the pixelsize is measured as the ink droplet ejection characteristic, but theinvention is not limited to the method. For example, at these steps, theejection speed of each of ink droplets ejected from the nozzle openings13 . . . may be measured, and the condition for the re-polarization step(S46) and the condition for the spot heating step (S56) may be set basedon the measured ejection speed. The ink amount ejected from each of thenozzle openings 13 . . . may be measured and the condition for there-polarization step (S46) and the condition for the spot heating step(SS6) may be set based on the measured ink amount.

The methods of the third and fourth embodiments are methods of changingthe polarization degree of the piezoelectric material 29, therebyadjusting the displacement amount of the drive vibrator 24B, 24C. Thesemethods can also be applied to a liquid jet head in which apiezoelectric vibrator (piezoelectric vibrator of so-called deflectionvibration mode) is provided directly in the diaphragm part 20 of thepressure chamber 15.

In each of the above-described embodiments, the ink jet recording head 1used in an image recording apparatus has been taken as an example of aliquid jet head. The scope of the invention is not limited to therecording head 1. For example, the invention can also be applied toliquid jet heads designed for industrial machines including, but notlimited to, an optical filter manufacturing apparatus, a stamping ormarking apparatus, and a microdispenser. The liquid jet heads, each ofwhich uses highly durable piezoelectric vibrators, can be used stablyover a long term.

As described above, according to the invention, the following advantagesare provided: The piezoelectric vibrator unit of the invention ismanufactured through the displacement amount measurement step ofmeasuring the displacement amount of each of the piezoelectric vibratorswith respect to the reference voltage, and the displacement amountadjustment step of setting a treatment condition for each piezoelectricvibrator based on the measurement result by the displacement amountmeasurement step and executing displacement amount adjustment based onthe setup condition for making the displacement amounts of thepiezoelectric vibrators uniform. Thus, the displacement amounts of thepiezoelectric vibrators can be made uniform, and accordingly, the liquidejection characteristic of the liquid jet head can be made uniform.

Since the displacement amounts are adjusted after the separatepiezoelectric vibrators are obtained, the displacement amount of eachpiezoelectric vibrator is less likely to be changed after the adjustmentis low. Therefore, additional, wasteful steps, such as re-adjustment,etc., can be dispensed with, and manufacturing can be made efficient.

Further, even the piezoelectric vibrator unit which had to be handled asbeing defective formerly can be mounted on a product after beingsubjected to the adjustment. Accordingly, the manufacturing yield canalso be raised.

If the displacement amount adjustment is trimming treatment of trimminga portion of the active region of the external electrode in eachpiezoelectric vibrator, the displacement amount of each piezoelectricvibrator can be adjusted to any desired displacement amount depending onhow the operational range of the outermost piezoelectric material isgiven. Thus, the displacement amounts of the piezoelectric vibrators canbe made uniform. Since the displacement amounts of the piezoelectricvibrators are made uniform, the ejected ink droplet amounts can be madeuniform with good accuracy among the nozzle openings, and the imagequality can be enhanced.

If the trimming treatment is to trim the portion of the active region ofthe external electrode by executing laser beam machining, the trimmingcan be easily accomplished with high accuracy.

When the outermost piezoelectric material is made thicker than any otherpiezoelectric material, the thick outermost piezoelectric materialprotects the internal electrodes even if the trimming reaches the thickoutermost piezoelectric material. Accordingly, the piezoelectricvibrator unit can be mounted to a product reliably. Therefore, themanufacturing yield of the piezoelectric vibrator unit can be raised.

If prior to the displacement amount measurement step, semi-saturationpolarization treatment in which polarization is stopped beforesaturation to put the piezoelectric material in a semi-saturationpolarization state, is executed, and the displacement amount adjustmentis executed by re-polarization treatment of again polarizing thepiezoelectric material of the semi-saturation polarization state in theforward direction, the polarization direction becomes one direction tothe saturation side. Thus, the piezoelectric material can be easilyadjusted into any desired polarization state. Therefore, thedisplacement amounts of the piezoelectric vibrators can be easily madeuniform, and manufacturing can be made efficient. In this method, thephysical shape of each piezoelectric vibrator before the adjustment andthat after the adjustment do not change and thus also in this point, thedisplacement amounts of the piezoelectric vibrators can be reliably madeuniform.

If the semi-saturation polarization state is set to a polarization stateof 90% of the saturation polarization state, adjustment is easy, and anecessary and sufficient margin can be provided.

If prior to the displacement amount measurement step, saturationpolarization treatment of executing polarization to saturation to putthe piezoelectric material in the saturation polarization state isexecuted, and the displacement amount adjustment is executed by spotheating of locally heating the piezoelectric material of the saturationpolarization state, the heated portion is locally depolarized.Accordingly, the piezoelectric material can be adjusted in any desiredpolarization state. The heating temperature in the heated portion andthe heated portion area can be changed, to change the depolarizationdegree and the depolarized portion area. Accordingly, fine adjustmentcan also be realized. Thus, the displacement amounts of thepiezoelectric vibrators can be made uniform easily and precisely. Inthis method, the physical shape of each piezoelectric vibrator beforethe adjustment and that after the adjustment do not change, and thusalso in this point, the displacement amounts of the piezoelectricvibrators can be reliably made uniform.

If the displacement amount adjustment is executed by heatingpolarization adjustment of supplying a polarization drive signal to theelectrode for charging and discharging the piezoelectric materialalternately for causing the piezoelectric vibrator to generate heat byitself and polarizing the piezoelectric material of the heat generationstate of the piezoelectric vibrator, the piezoelectric vibrator can beheated without providing a heating unit. Further, the piezoelectricvibrator to be adjusted can be selectively heated.

The liquid jet head of the invention is manufactured through theejection characteristic measurement step of measuring the ejectioncharacteristic of liquid ejected from the nozzle openings by applyingthe same drive signal to all piezoelectric vibrators for each of thenozzle openings, and the ejection characteristic adjustment step ofsetting a treatment condition for each piezoelectric vibrator based onthe measurement result at the ejection characteristic measurement stepand making displacement amount adjustment to the piezoelectric vibratorsbased on the setup condition for making the liquid ejectioncharacteristics of the nozzle openings uniform. Thus, the liquidejection characteristics of the nozzle openings can be made uniform.

At this time, adjustment can also be made to variation factors otherthan the drive vibrators. For example, variations in the joint state ofthe drive vibrator to the island part, variations in size of the nozzleopening, variations in shape of the pressure chamber, etc., can also becorrected. Since the displacement amounts are adjusted at the last stageof the manufacturing step of the recording head, wasteful steps, such asre-adjustment, etc., can be dispensed with, and manufacturing can bemade efficient.

Further, even a liquid jet head which had to be handled as beingdefective formerly can be mounted on a product after being subjected tothe adjustment, and the manufacturing yield can be raised.

If the piezoelectric vibrators are manufactured by laminatingpiezoelectric material and internal electrodes alternately to provide alaminate substrate, forming an electrode layer on the surface of thelaminate substrate to provide a laminate member having an externalelectrode, and cutting the laminate member to have the piezoelectricvibrators in the form of teeth of comb, the displacement amount of eachpiezoelectric vibrator can be adjusted in the state of the finishedproduct of the vibrator unit. Therefore, the adjustment can be conductedeasily and reliably, and the piezoelectric vibrator unit manufacturingyield can be raised.

1. A manufacturing method of manufacturing a piezoelectric vibrator unitcomprising a plurality of piezoelectric vibrators, the plurality ofpiezoelectric vibrators to which a drive signal is to be applied so thatthe plurality of piezoelectric vibrators are displaced in a direction,the plurality of piezoelectric vibrators including a first piezoelectricvibrator and a second piezoelectric vibrator each of which includes apiezoelectric material, the manufacturing method comprising: supplying apolarization drive signal, which is different from the drive signal, forcharging and discharging the piezoelectric material alternately, to theplurality of piezoelectric vibrators so as to generate self-heating;after supplying the polarization drive signal, supplying a polarizationvoltage in the direction to the plurality of piezoelectric vibrators inwhich the self-heating is generated so as to polarize the plurality ofpiezoelectric vibrators; measuring a displacement amount of each of theplurality of piezoelectric vibrators after supplying the polarizationvoltage; setting a target displacement amount based on the measuringresult, wherein the displacement amount of the first piezoelectricvibrator is less than the displacement amount of the secondpiezoelectric vibrator, and the target displacement amount is thedisplacement amount of the first piezoelectric vibrator; calculating adifference between the displacement amount of the second piezoelectricvibrator and the target displacement amount; setting a condition of aspot heating for the second piezoelectric vibrator based on thedifference, the condition including a heating area, a heating time and aheating temperature at which the piezoelectric material of the secondpiezoelectric vibrator is depolarized and which is equal to or higherthan Curie temperature; and performing the spot heating by applying alaser beam to a portion of the piezoelectric material of the secondpiezoelectric vibrator based on the condition so that the portion of thepiezoelectric material of the second piezoelectric vibrator isdepolarized and the displacement amount of the second piezoelectricvibrator is decreased.
 2. The manufacturing method of claim 1, wherein alaminate structure of each of the plurality of piezoelectric vibratorsincludes common internal electrodes and segment internal electrodeslaminated alternately with a layer of the piezoelectric materialinterposed between adjacent pair of the common and segment internalelectrodes to form an active region in a free end part.
 3. Themanufacturing method of claim 2, wherein each of the plurality ofpiezoelectric vibrators is displaced in a direction orthogonal to alamination direction by the action of an electric field.
 4. Themanufacturing method of claim 2, wherein each of the plurality ofpiezoelectric vibrators is disposed in a lamination direction by theaction of an electric field.
 5. The manufacturing method of claim 2,further comprising: laminating piezoelectric material layers andinternal electrode layers alternately to provide a laminate substrate;forming an external electrode layer on at least a surface of thelaminate substrate to provide a laminate member; and at least partiallycutting the laminate member to provide comb-like piezoelectricvibrators.
 6. The manufacturing method of claim 1, wherein each of theplurality of piezoelectric vibrators has, at least in part, a laminatestructure of electrodes and at least one layer of piezoelectricmaterial.
 7. The manufacturing method of claim 1, wherein displacementamounts of each of the plurality of piezoelectric vibrators are measuredby applying a reference voltage to each of the plurality ofpiezoelectric vibrators.
 8. The manufacturing method of claim 1, whereinthe polarization signal has a preset waveform and is supplied to chargeand discharge the at least one of the plurality of piezoelectricvibrators to generate the self-heating.